Modeling wheat growth to determine economic feasibility under deficit irrigation and nitrogen management strategies

The sustainability of any agricultural system depends on economical and feasible use of crop inputs to earn the highest net margin. The fertilizers are the essential inputs for crop production, particularly under varying irrigation conditions. To examine these essentials for wheat production, multi-seasonal experiments on varying levels of deficit irrigation and nitrogen applications were conducted for determining their economic feasibility through modeling applications. The experiment involved two irrigation levels [FI=full irrigation (341.6 mm, equivalent to soil-based crop water requirement), DI80 = 80 % of FI (273.3 mm, deficit irrigation)] and two levels of liquid nitrogen fertilizer (LNF) (N:P:K=32:0:0), labelled as LNF100 (434 Lha−1, 100 % of nitrogen dose) and LNF75 (325.5 Lha−1, 75 % of nitrogen dose). The highest grain yield (5.75 t.ha−1), dry matter (14.38 t.ha−1) and plant height (101.3 cm) were achieved under FI.LNF100. However, this treatment had lower water productivity compared to DI80.LNF100 (1.69 vs. 2.00 kgm-³). The SALTMED model effectively simulated these dynamics, showing high accuracy and reliability during both calibration and validation phases, with low RMSE for grain yield (0.23–0.29 t.ha−1), dry matter (0.45–0.93 t.ha−1), plant height (1.1–1.89 cm) and soil moisture (0.68–0.75 %). Moreover, the NRMSE varied from 0.11–0.24, R² varied from 0.95–0.85, CRM varied from −0.003–0.05. Additional hypothetical scenarios, including reduced irrigation levels (DI60 and DI50) and increased nitrogen doses (up to LNF200) indicated that optimal yields and dry matter were achieved at LNF150–LNF175, beyond which yields declined. These findings highlight the importance of balanced nutrient management under diverse irrigation conditions. Economic analysis of all scenarios revealed FI.LNF150 (full irrigation with 150 % nitrogen dose) as the most profitable strategy, generating the highest net margin (826 US$ha−1) and BCR (1.44), while DI80LNF175 maximized water economic productivity (0.69 US$m⁻³). Results indicate two viable optimization strategies for semi-arid wheat systems: (1) FI.LNF150 for maximal profitability and (2) DI80.LNF175 for water-limited conditions, with selection dependent on resource prioritization.